Circuit breaker install, before or after cut off switch?

blackwood

Adventurer


Everything will be located in my pickup truck's bed minus the starting battery. The isolator and second battery will be right next to each other. Do I still need to install some sort of fuse between the two?
 

DaveNay

Adventurer
In general, you should try top place the circuit breaker as close to the source of power as is possible/practical. I would try to move the circuit breaker into the engine compartment near the battery and ahead of the battery cut off switch in the bed of the truck.

The reason for having the breaker close to the power source is to get maximum protection for the entire wire run. This prevents more serious problems if there is damage to the wire between the battery and the truck bed.
 

DaveNay

Adventurer
That does make sense. I also have an extra fuse holder on hand.

If you have a second fuse holder, then I would do it like this:

Starter battery -> circuit breaker -> long wire run -> disconnect switch -> isolator -> second battery -> fuse -> fuse block

If the fuse block also has a master fuse, then you will have redundancy with the inline fuse and you could eliminate the inline fuse.
 

DiploStrat

Expedition Leader
Takes TWO to Tango

Yes, you need a fuse on EACH end of that line as it is live from each battery. The reason being that the cable running from your starter battery back to the truck bed is, in effect, a 20 foot arc welder, powered by either or both batteries.

If you had both batteries under the hood, within eighteen inches of each other, then you could skip the fuse.

These are excellent as they attach directly to the positive terminal of each battery: https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Not sure of the purpose of the Battery Cut Off switch between the starter and camper batteries. Normally such a switch, if needed, goes between the camper battery and your camper loads.

P.S. You may wish to review some of the posts in this forum and check your charging voltage to see if you really need a B2B.
 
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blackwood

Adventurer


Alright, new revision. Fuses on both end of wiring. I forgot why I bought the battery cut off in the first place but it was to kill switch to turn off any accessories that would be in the truck bed. Just in case I forgot and left something on. The breaker does have a shut off built in so I could pop the hood and hit the switch if I wanted to stop the feed.

I plan on adding solar panel at a later time. This is just to get me some juice for a trip this month.
 

DiploStrat

Expedition Leader
You shouldn't need a fuse between the camper battery and the fuse bloc; it is, of course, full of fuses! A kill switch is a reasonable option.

What kind of truck are you using? If your charging system runs at 14v or more, you will get MUCH better performance, i.e. a faster charge, out of a properly sized relay based system, either key controlled or automatic.

If you must use a D250S, then add the SmartPass, otherwise you are limiting your charge to only 20A or less. Lifelines like a charge rate of up to 5C, not the more common C/5.

The combination of the D250S and a SmartPass is expensive, but it does include a solar controller at no extra cost and it does assure a high charge voltage during the low amp absorb stage. (Just costs a lot of money and takes up a lot of space.)
 

blackwood

Adventurer
My Toyota truck runs at about 13.7v. We have another Toyota SUV and its the same voltage while running. The Ctek D250s does boost the voltage up to 14.4v which is good. I can't throw more money into this install at this time with a Smartpass module for up to an 80A charge. I'm already over budget with my total build, the D250S and its 20A charge will have to do for now. The D250s does have a built in MPPT solar charger. My power usage is pretty low. I'll just have some reading lights, camera/device battery charging, vent fans, etc. No fridge.

I already have all of the other items minus an AGM deep cycle battery. I have a Costco group 27 marine battery at home at my disposal that is on a battery tender but I'm no so sure about using that non sealed battery in the enclosed space with my truck shell, I'll be sleeping back there. Lifeline seemed to be the way to go only costing a little bit more than other AGM batteries. I'm open to other brands and possibly smaller sizes.
 

DiploStrat

Expedition Leader
This may save you some money on the CTEK. http://www.hkbelect.com/products/toyota/ (Recommended by a very savvy Toyota owner who runs a Blue Sea ACR.) Some explanation: http://www.hkbelect.com/faq/

Agreed on the fuse between battery and fuse box; I am assuming that the two are within 18 inches of each other.
 

blackwood

Adventurer


I already all of the components on hand and I'm in the process of tackling most of it this weekend.

That fuse does look cool to get the voltage up but $50 is asking a lot for soldering on a few components :Wow1: All of the parts would cost them under $1 to build. If I find a DIY tutorial later, I'm going to build one myself to test out.
 

DiploStrat

Expedition Leader
Ask and ye shall receive: http://www.smartgauge.co.uk/alt_mod.html The advantage of a commercial product is that this one keeps the fuse and this one is fully adjustable: http://www.mechman.com/accessories/voltage-control-modules/adjustable-voltage-boost-module-for-oval-3-pin-toyota/

After long arguments with dwh I was surprised to learn that some modern Toyotas run at such low voltages. I actually like the D250S/SmartPass combo, especially if it allows you to save on a solar controller. For best results be sure to:

-- Install the temperature sense option, and,

-- Install the voltage sense option if your D250S is any distance from the camper battery.
 
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